Silicon nitride thin films as a dielectric layer have been widely used in semiconductor fabrication processes. For example, SiN films are used in multi-patterning processes as spacer materials to achieve smaller device dimensions without employing the most expensive EUV lithography technology. Additionally, SiN can be used as a gate spacer material to isolate gate structure and contact areas to minimize potential leakage current.
Traditional silicon nitride spacer fabrication processes include conformal SiN film deposition on 3D structures (e.g., fins) followed by directional plasma dry etching to remove the top and bottom layer while keeping the sidewall film as a spacer. However, it has been found that the dry etch process could damage the sidewall surface and change the film properties; eventually affecting device performance and yield.
Therefore, there is a need in the art for processes of depositing a selective spacer films.